1. A mixed integer program is a linear program with integral restrictions on some or all variables. a. True C. False For questions 29 : There are three projects. Binary variables X1,X2, and X3 are defined as follows: Xi=1 if project i is selected, and Xi=0 if project i is not selected, for i=1,2,3. 2. Write a constraint to represent: "At least one of the three projects must be selected." x1+x2+x31 3. Write a constraint to represent: "Between project 1 and project 2, exactly one must be selected." x1+x2=1 4. Write a constraint to represent: "At most two projects of the three can be selected." x1+x2+x3=1, and Y1=0 if X1=0. 10. What does the expression " 780Y," " mean? a. The expense of the fixed charge is $780. 6. The $780 fixed charge is spent if Y1=1; and $780 is not spent if Y1=0. c. It is the total cost of producing product 1 , including both fixed and variable costs. 11. Write a constraint to represent: "If X1=0 then Y1=0." x1+41=780 12. Write a constraint to represent: "If X1>=1 then Y1=1," x1+41780